Patent literature 1 describes a known glass substrate including a surface with asperities. A smooth surface of a substrate is patterned by etching to form a pattern with a concave-convex area, thereby manufacturing such a glass substrate. More specifically, the surface of the glass substrate is etched to form a recess of the pattern with a concave-convex area to a depth smaller than a certain depth while an unetched area of the surface of the glass substrate becomes a protrusion. Next, a planar indenter with a smooth and flat surface is made to contact the protrusion tightly. The indenter is then pressed to form a compressed layer in the protrusion. Next, the indenter is removed and the glass substrate is etched with an acidic etchant to etch the compressed layer and an uncompressed layer except the compressed layer at different etching rates. As a result, the pattern with a concave-convex area having the recess of the certain depth is formed in the surface of the glass substrate.
However, this manufacturing method is not suitable for formation of fine asperities as it uses an indenter. This manufacturing method further encounters a problem of bad mass productivity as it cannot control a concave-convex area precisely because of direct processing on the glass substrate.
Patent literature 2 describes a known glass substrate with a light-scattering film that gives asperities to a glass substrate without processing the glass substrate directly. This glass substrate with a light-scattering film includes a light-scattering film composed of a silica-based film containing light-transmitting fine particles that is formed on a main surface of the substrate by sol-gel process. More specifically, the fine particles in the light-scattering film form at least secondary particles and the surface of the light-scattering film is given asperities reflecting the fine particles and the secondary particles.